A/D conversion is important in a wide variety of applications. Many different circuits may be used to convert analog signals to digital signals. These ADC circuits have many drawbacks.
For example, in pipelined A/D circuits (ADC) that share operational amplifiers (op-amps) between stages, errors may be introduced. More specifically, a charge injection error voltage at the op-amp input node may be introduced. This causes a large offset voltage as the charge injection error voltage is added with the intrinsic offset voltage of op amp. The large offset voltage may affect the precision of the ADC.
Also, as the process technology is scaled down, Fliker (1/f) noise becomes more critical as the corner frequency tends to increase.